Four-wire circuit



l. MILLS.

FOUR-WIRE CIRCUIT.

APPLICATION FILED JUNE 7, 1918.

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I Y I33 l.. C... v

IN V EN TOR.

A TTORNEY Patented Sept 14, 1920.

ings cooperate in inducing a corresponding impulse in the winding 2% whence it passes to the station A through theamplifier 25.

It will be observed from the circuits above traced that talking in either direction is accomplished over all four wires of the four-wire circuit. In such a circuit as this, even without the use of the balancing networks N and the transformers 10, 11, 12 used in connection therewith, the amplification of thecurrent may be made such as to producea-t the re ceiving end-nearly or quite as strong a talking current as is sent out at the-opposite end of the line. The degree of amplification possible in the ordinary repeater circuit is very limited owing to the impossibility of accurately. and fully balancing the line at 4 the repeater station by the artificial net workfand singing will result if the amplification is made unduly'great. With the circuit hereinabove described, even disregarding the degree of balance obtained by networks N, there will vbe no singing if the total attenuation of the two circuits between A and. B is greater in any degree than the sum of the gains of the one-way amplifiers. By using a fair degree of balance at N. N. an even high amplification may be had without singing so that stronger talking currents may be received than are emitted at the sending station.

' What I claim is:

' l. A transmission system comprising two pairs of conductors extending between stations a connection at one station delivering current substantially equally to said pairs iii parallel, a connection at another station delivering current to two circuits in parallel each of which comprises one conductor of each of sa d pairs, means at each station for taking off current delivered by the other, and amplifiers for the currents traveling in.

either direction.

' 2; A transmission system comprisingitwo pairs of conductors extending between two stations an amplifier at one station delivering current equally to said pairs in parallel an amplifier at the other station delivering current to two separate circuits in parallel each of which comprises one conductor of each'of 'saidpairs, and means at each'station 'for taking off the current delivered at the other.

7.3. In a transmission system for connect- 'ing a plurality of stations a two-wire circuit at each stationfour conductors extending between the Stations, an outgoing 'connec tion at each station for uniting the two-wire circuit with the four conductors in a 'defi-f conductors extending between stations, a

one-way amplifier'at each station, electrically connected on one side to all four vof said conductors and on-the other side to the station and another connection from each station to said four conductors, the con nection of said amplifiers to the four conductors being diiierent at each station and each corresponding to the said other connection at a difi'erentstation.

5. In a transmission system for connecting two signal stations, an incoming and an outgoing connection at each station, at least one amplifier at each station located in saidconnections,-two complete loops extending between the stations and means,

uniting said loops and said connections, for distinguishing between currents originating at "different stations whereby signal impulses from the outgoing connection at one station enter only the incoming connection at the other station.

6. In a'tran smission system for connecting two signal stations, a two-wire circuit at each station, two pairs of conductors extending between the stations, transformer windings bridging the respective pairs- .at each station, an outgoing connectionirom one station having a conductor running to .themid-point of each of said transformer windings at that station and an incoming connection at the other station having similar connection to the transformer windings at that station, an outgoing connection from said other station having a winding in inductive relation to each of the said transformer windings at that station and an incoming connection at the first nanied station having similar relation to the transformer windings of said first named sta- 

